Hypothyroidism is the condition that reflects decreased concentrations of thyroid hormones, due to any cause. The resulting hypometabolic state causes decreased heat production and generally slows many of the bodies' processes. Its prevalence is 1 to 3 percent of young to middle-aged adults, mainly women, and its incidence rises with age. Severe hypothyroidism occurs in 2 to 4 percent of women older than seventy years of age, and milder forms of disease in 8 to 15 percent. Outside of North America, iodine deficiency is a major cause of hypothyroidism. In the United States, causes include Hashimoto's disease and treatment of hyperthyroidism—either by surgery or radioactive iodine (I-131). Treatment for hypothyroidism consists of hormone supplementation, generally synthetic l-thyroxine, taken once per day.
MARTIN I. SURKS
Shapiro, L. (1999). "Hypothyroidism." In Atlas of Clinical Endocrinology, Vol. 1: Thyroid Diseases, ed. M. I. Surks. Philadelphia, PA: Current Medicine.